Electrolytic process



JAMES ROBERT STACK, or PERTH on, NEW JERSEY, ASsIGNoR TO AMERICA SMELTING AND REEImNG COMPANY; OF NEW YORK, N. Y., A CoRPoRA'rIoN on NEW JERSEY;

ELECTROLYTIC PROCESS.

No Drawing. Application filed December 80, 1920, Serial No. 484,114. Renewed January 14, 1924;

To all whom it may concern:

Be it known that I, J AMES RoBER'r STACK, a citizen of the United States, and resident of Perth Amboy, in the county of Middlesex and State of New Jersey, have invented certain new and useful Improvements in Electrolytic Processes, of which the following is a specification.

The invention relates to certain new and useful improvements in the production of electrically refined tin from impure .tin cast in the form of anodes and to an improved form of electrolyte suitable for the process hereinafter featured.

It is suggested in the application of Harry H. Alexander, Serial No. 434,124, filed under even date, that an electrolyte be produced from the impure tin of such a character the it will insure the continued maintenance )fthe electrolytic deposition of the tin during the refining operation and which will itself be devoid of lead and other I detrimental impurities usually present in the tin to be refined. It has been known to use sulphuric acid for the purpose of precipitating the lead present and to use hydrofluosilicic acid to dissolve the tin from the anodes without the formation of the basic A salts of tin. In the Alexander application it is suggested that the amount of sulphuric acid be increased over the amount necessary to combine with the lead present and that the amount of hydrofiuosilicic acid heretofore used in such electrolytes be correspondingly reduced in amount.

It is further suggested in the application of Clarence P. Linville, Serial No. 434,118, filed under even date, that the electrolyte be improved by the addition of free hydrochloric acid or by sodium chloride in the for the tin.

The invention features economy in cost of operation not only in connection with the cost of the reagent materials in the electrolyte but also in the amount of electric current used per unit mass of tinde-' posited and in the amount of waste mate rial necessary to handle.

Accordingly, one of the objects of the invention is to provide an electrolyte which will possess the desirable characteristics inherent in the electrolytes featured in the above identified applications, Such as ready solubility of the anodes, elimination of polarization, continuity of action, and the obtaining of a good deposit of tin which will be smooth, dense and. adherent but that these results be affected by the use of a cheaper material than the hydrofluosilicic acid heretofore used.

I attain this phase of the invention by substituting for the hydrofluosilicic acid heretofore used one of the cheap cresol sulphonic acids. phonic acid can be used in this connection for a dual purpose, first, as an addition agent in place of or in part substitution for the glue and cresylic acid addition agents, and second, to replace the hydrofluosilicic acid, either in whole or inpart.

One form of sulphonic acid which has given entire satisfaction is made bysulphonating crude cresylic acid with stro sulphuric acid but it is to be understo that this form of sulphonic acid is merely suggestive.

The sul honic acid can be prepared from benzol, p enol cresol, and crude cresylic acid; the best results having beenobtained with phenol sulphonic acid, cresol sulphonic acid and a mixture of benzo'l and phenol sulphonic acid.

Addition agents, such as glue and cresylic acid may be used but the amount of these addition agents necessa to effect the desired results has been foun to be less than in the former methods where hydrofluosilicic acid was used as the tin solvent. It, hasalso been found in practice that one to two per cent by weig t of sulphonic acid is entirely satlsfactory when used in connection with hydrofluosilicic acid but in case the latter acid is eliminated an equivalent larger amount of ,the sulphonic acid is necessary. An amount as h gh as fifteen per cent by weight of sulphomc acid It has been found that sullil has been used with entire satisfaction where the hydrofluosilicic acid has been omitted but ten per cent by weight is suggested in this case.

Une form of electrolyte which is at pres-. ent in use, analyzes as follows:

'lin 4.0% b weight in ous form; sulphuric acid SUQ 5.0% by Weight; sulphonic acid 2.0% by weight; hydrofluosilicicacid (ll'LSiF 2.0% by weight; hydrofluoric acid (HF) 0.6% by weight due to decom osition of H Sil hydrochloric acid (Hill) 0.2% by weight; sodium sulphate (NaSOQ) due to addition of NaCl; addition agents glue, cresyli acid, etc.

With the addition of sulphonic acid it is possible to maintain the continuity of the electrolytic process with a smaller percentage of tin in solution than has been known heretofore thus avoiding a possible source of waste in tin lost in the precipitates. lt is suggested that about two to four per cent of tin in the ous state gives the most satisfactory results and tin in this state has the additional advantage in that reduced-power may be used than where the tin is in the ic form.

Still featuring economy of production it is required that the least possible amount of electric current be used. As the amperage necessary to efiect the operation is theoretically fixed at about eight amperes per square foot of cathode surface, the only possible way to edect a saving. in power used, aside from the observing of good electrical ractioe, is to reduce the voltage. Hereto ore when the recess was carried on under temperature 0 -70 the voltage per tank was to volts and only about 50% of the anode was dissolved before adherin slimes prevented further anode corrosion. t is found, however, that the heating of the electrolyte not only improved the process but permitted as much as a fifty per cent drop in voltage necessary. -l or instance, it was found that the heating oil the electrolyte to maintain a temperature of approximately 95 F. had the eldest of permitting a drop in voltage to 0.2 to 0.25 volts, thus eflecting a material saving in ower with resulting chea-pness oil operation.

n addition to this is was possible to dissolve to of the anodes before they weenie too thin for effective work. Heating of the electrolytic solution was also found to assist in preventing the formation of outgrowths upon the cathode surface and in general a better anode corrosion was maintained, better conductivity was provided and in neral an improved deposit was attained.

1aving thus described my invention, .l c aim: I

1. In the electrolytic refining of impuretin containing lead, the process oil preventing conation oil the tin deposited from nannies the impure tin anode upon the cathode,

which consists in employing as the electrolyte a solution of tin in sulphonic acid and a protective agent sufficient to convert the lead contained in the dissolving tin anode into a compound insoluble in the electrolyte.

2. In the electrolytic refining of impure tin containing lead, the process of preventing contamination of the tin deposited from the impure tin anode upon the cathode, which consists in employing as the electrolyte a solution of tin in a mixture of sulphonic and sulphuric acids.

3. In the electrolytic refining of impure tin, the process of producing an appropriate electrolyte for the refining operation which consists in passing an electric current of suitable voltage and amperage from the impure tin as an anode to a cathode through a solution containing sulphuric acid to five per cent and sulphonicacid two to four per cent.

l. In the electrolytic refining of impure tin containing lead, the process of preventing contamination of the tin deposited from the impure tin anode upon the cathode,

which consists in employing as the electrolyte a solution of tin in hydrofluosilicic acid and which contains sulphonic acid.

5. In the electrolytic refining of impure tin containing lead, the process of prevent ing contamination of the tin deposited from the impure tin anode upon the cathode, which consists in employing as the electrolyte a solution of tin in a mixture of sulphonic, sulphuric and hydrofiuosilicic acid.

6. ln the electric refining of impure tin containing lead, the process of preventing contamination of the tin deposited from the impure tin anode upon the cathode, which consists in employing as the electrolyte a solution of tin in a mixture of sulphonic and sulphuric acids and an addition agent.

7. In the electrolytic refining of impure tin containing lead, the process of prevent ing contamination of the tin deposited from the impure tin anode upon the cathode, which consists in employing as the electrolyte a solution of tin in sulphuric acid approximately two to five per cent by weight, sulphonic acid approximately one to two per cent by weight and hydrofluosilicic acid approximately two per cent by weight.

8. ln the electrolytic refining of impure tin containing lead, the process which consists in employing as the electrolyte a solution of tin, two to four per cent by weight in the ous form together with sulphonic acid and a protective agent sufficient to convert the lead present in the electrolyte into a a compound insoluble in the same.

9. In the electrolytic refining of impure tin containing lead, the process which consists in employing as the electrolyte a solution of tin together with sulphonic acid and iii lid

' in hydrofluosilicic acid in an amount approximately two to four per cent of tin by weight and containing sulphonic acid approximately one to two per cent by weight.

12. An electrolyte for the deposition of tin free from lead com rising an electrolytic solution of tin in by rofluosilicic acid approximately two to four per cent of tin by weight and containing a protective agent in an amount sufficient to convert the lead into a compound insoluble in the electrolyte and sulphonic acid.

13. An electrolyte for the deposition of tin free-from lead comprising an electrolytic solutlon of tin in hydrofluosilicic acid approximately two to four per cent of tin by weight and containing a protective agent 7 in an amount sufiicient to convert the lead into a compound insoluble in the electrolyte and sulphonic acid approximately one to two per cent by weight and an addition agent.

14. An electrolyte containing sulphonic, sulphuric and hydrofluosilicic acids together with an addition agent.

15. In the electrolytic refining of impure tin containing lead, the process which consists in employing as the electrolyte a solution of tin, two to four per cent by weight in the ous form together with sulphonic acid and a protective agent sufiicient to convert the lead present in the electrolyte into a compound insoluble in the same and an agent capable of forming hydrochloric acid under the conditions present.

16. In the electrolytic refining of impure tin containing lead, the process which consists in employing as the electrolyte a solution of tin, two to four per cent by weight in the ous form together with sulphuric acid in excess of the amount suflicient to convert the lead present into an insoluble compound and a halogen salt capable of reacting with the" excess of sulphuric acid to form a free halogen acid.

17. In the electrolytic refining of impure tin containing lead, the process which consists in employing as the electrolyte a solution of tin, two to four per cent by weight in the ous form together with sulphuric acid in excess of the amount suflicient to convert the lead present into an insoluble compound and asodium chloride.

18. An electrol to for the. deposition of tin free from lead comprising a solution of tin in hydrofluosilicic acid, and containing sulphuric acid in an amount in excess of the amount necessary to precipitate the lead present, a halogen salt capable of reacting with the excess of sulphuric acid to form a free halogen acid, sulphonic acid and an addition a ent.

19. An e ectrolyte for the deposition of tin free from lead comprising a solution of tin in hydrofluosilicic acid and containing sulphuric acid in an amount in excess of the amount necessary to precipitate the lead present, a halogen salt capable of reacting with the excess of sulphuric acid to form a free halogen acid and an addition agent.

20. In the electrolytic refinin of impure tin containing lead, the metho of producing an appropriate electrolyte for the refining operation, which consists in passing an electric current of suitable voltage and amperage from the impure tin as an anode to a cathode through an electrolyte which is a solvent of tin and lead, and protecting the electrolyte from contamination by lead,

by incorporating with the electrol e anagent which will combine with the ead to form an insoluble compound together with sulphonic acid while subjecting the electrolyte to a temperature higher than room temperature.

21. In the electrolytic refining of impure tin containing lead, the method ofproducing an appropriate electrolyte for the refining operation, which consists in passing an electric current of suitable voltage and amperage from the impure tin as an anode to a cathode through an electrolyte which is a solvent of tin and lead, and protectin the electrolyte from contamination by -lea by incorporating with the electrol an agent which wil combine with the ead to form an insoluble compound together with sulphonic acid while subjecting the electrol e to a temperature approximately 95 22. In the electrolytic refining of impure tin containing lead'the method of produc- I ing an appropriate electrolyte for the refinin operation which. consists in passing an e ectric current at approximately 0.2 to

tin containing lead, t emethod of producing v an appropriate electrolyte for the refining operation which consists in passing an electric current at approximately 0.2 to 0.25 volts from the impuretin as an anode to a cathode throu h an electrolyte containing sulphonicacid, protecting the electroing iyte from contaation by lead and. heating the electrolyte during the passage of the electriccurrent. 24. In the electrolytic refining of impure tin containing lead, the method of produce an appropriate electrolyte .for the re-' finlng operation, which consists in passing an electric current at approximately 0.2 to 0.25 volts from the impure tin as an anode to a cathode through an electrolyte containing sulphonic and sulphuric acid and heating the electrolyte during the electrolytic action. c

250 l the electrolytic refining of impure tin containing lead, the method of producing an appropriate electrolyte for the refining operation, which consists in passing an electric current at approximately 0.2 to

0.25 volts from the impure tin as an anode to a cathode through an electrolyte containing sulphonic hydrofiuosilicic acid and sulphuric acid and heating the electrolyte during the electrolytic action. I

26. In the electrolytic refining of impure tin containing lead, the method out producing an appropriate electrolyte for the refining operation, which consists in passing an electric current at approximately 0.2 to

0.25 volts from the impure 7 tin as an anode to a cathode through an electrolyte containin sulphonic and sulphuric acid and heating t e electrolyte during the electrolytic action to a temperature of approxi- -inately 95 F. v

2?, In the electrolytic refining ofirnpure tin containing lead the method of producnet-eater ing an appropriate electrolyte for the refining operation, which consists in passing an electric current at approximately 0.2 to 0.25 volts from the impure tin as an anode to a cathode through an electrolyte capable of dissolving the tin in the anode While precipitating the lead and heating the electrolyte during the electrolytic tin dissolving step.

28. In the electrolytic refining of impure tin containing lead, the method of produc ing an appropriate electrolyte for the refining oper-ation, whichconsists in passing an electric current at approximately 0.2 to 025 volts from the impure tin as an anode to a cathode through an electrolyte capable of dissolving the tin in the anode While precipitating the lead and heating the electrolyte during the electrolytic tin dissolving step to a temperature of approximately 95 l1.

' 29. In the electrolytic refining of impure tin the method of producing an appropriate electrolyte for the refining operation Which consists in passing an electric current of relatively low voltage from the impure tin as an-anode to a cathode through an electrolyte capable of dissolving the tin and subjecting the electrolyte to a temperature of approximately 95 F. during the passage of the electric current.

Signed at Perth Amhoy, in the county of Middlesex and State of New Jersey this 10th day or lD ecernloer A, D. 1920.

JAMES aonnar srnon, 

